Strut Interference Effects on Pitot Tube Velocity Measurements

2007 ◽  
Author(s):  
Sandra K. S. Boetcher ◽  
Ephraim M. Sparrow
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Body ◽  
Pitot Tube ◽  
Velocity Measurements ◽  
Measuring Device ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Velocity Measuring ◽  
The Impact

The possible impact of the presence of the strut portion of a Pitot tube on the efficacy of the tube as a velocity-measuring device has been evaluated by numerical simulation. At sufficiently low Reynolds numbers, there is a possibility that the precursive effects of the strut could alter the flow field adjacent to the static taps on the body of the Pitot tube and might even affect the impact pressure measured at the nose. The simulations were performed in dimensionless form with the Reynolds number being the only prescribed parameter, but the dimensions were taken from a short-shanked Pitot tube. Over the Reynolds number range from 1500 to 4000, a slight effect of the strut was identified. However, the variation due to the presence of the shank of the velocity measured by the Pitot tube operating in that range of Reynolds numbers was only 1.5%.

Flow in Locally Constricted Tubes at Low Reynolds Numbers

1970 ◽  
Vol 37 (1) ◽  
pp. 9-16 ◽  
Author(s):  
Jen-Shih Lee ◽  
Yuan-Cheng Fung
Keyword(s):  
Reynolds Number ◽  
Blood Flow ◽  
Shear Stress ◽  
Cylindrical Tube ◽  
Reynolds Numbers ◽  
Velocity Measurements ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Circular Cylindrical Tube ◽  
Velocity Pressure

With an objective to understand arteriosclerosis, the blood flow in a circular cylindrical tube with a local constriction is analyzed. Numerical results are presented for the streamlines and the distributions of velocity, pressure, vorticity, and shear stress in the Reynolds number range 0–25. These results have applications to other fluid-mechanical problems such as gauges for velocity measurements, etc.

Empirical Estimates of Body Drag of Large Waterfowl and Raptors

1988 ◽  
Vol 135 (1) ◽  
pp. 253-264 ◽  
Author(s):  
C. J. PENNYCUICK ◽  
HOLLIDAY H. OBRECHT ◽  
MARK R. FULLER
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Body ◽  
Number Range ◽  
Empirical Estimates ◽  
A Value ◽  
Body Drag ◽  
Wind Tunnel Measurements ◽  
Large Living ◽  
Performance Estimates

To whom reprint requests should be addressed. Measurements of the body frontal area of some large living waterfowl (Anatidae) and raptors (Falconiformes) were found to vary with the two-thirds power of the body mass, with no distinction between the two groups. Wind tunnel measurements on frozen bodies gave drag coefficients ranging from 0.25 to 0.39, in the Reynolds number range 145 000 to 462 000. Combining these observations with those of Prior (1984), which extended to lower Reynolds numbers, a practical rule is proposed for choosing a value of the body drag coefficient for use in performance estimates.

Low Reynolds numbers flow past an ellipsoid of revolution of large aspect ratio

1965 ◽  
Vol 23 (4) ◽  
pp. 657-671 ◽  
Author(s):  
Yun-Yuan Shi
Keyword(s):  
Reynolds Number ◽  
Aspect Ratio ◽  
Three Dimensional ◽  
Major Axis ◽  
Reynolds Numbers ◽  
The Body ◽  
Large Aspect Ratio ◽  
Low Reynolds Numbers ◽  
Ellipsoid Of Revolution ◽  
Limiting Case

The results of Proudman & Pearson (1957) and Kaplun & Lagerstrom (1957) for a sphere and a cylinder are generalized to study an ellipsoid of revolution of large aspect ratio with its axis of revolution perpendicular to the uniform flow at infinity. The limiting case, where the Reynolds number based on the minor axis of the ellipsoid is small while the other Reynolds number based on the major axis is fixed, is studied. The following points are deduced: (1) although the body is three-dimensional the expansion is in inverse power of the logarithm of the Reynolds number as the case of a two-dimensional circular cylinder; (2) the existence of the ends and the variation of the diameter along the axis of revolution have no effect on the drag to the first order; (3) a formula for drag is obtained to higher order.

A note on vortex streets behind circular cylinders at low Reynolds numbers

1971 ◽  
Vol 45 (1) ◽  
pp. 203-208 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Current State ◽  
Reynolds Number Range ◽  
Vortex Streets ◽  
Low Reynolds

A discussion is given of the current state of knowledge of vortex streets behind circular cylinders in the Reynolds number range 50 to 160. This was prompted by Gaster's (1969) report that he could not find the transition at a Reynolds number of about 90 observed by Tritton (1959) and Berger (1964a). A further brief experiment confirming the existence of the transition is described Reasons for rejecting Gaster's interpretation are advanced. Possible (mutually alternative) explanations of the discrepant observations are suggested.

Flow field behavior with Reynolds number variance around a spiked body

2016 ◽  
Vol 30 (30) ◽  
pp. 1650362 ◽  
Author(s):  
Shashank Khurana ◽  
Kojiro Suzuki ◽  
Ethirajan Rathakrishnan
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
The Body ◽  
Positive Pressure ◽  
Radius Of Curvature ◽  
Potential Candidate ◽  
Influence Zone ◽  
Number Range ◽  
Speed Flow ◽  
Basic Body

An experimental visualization study was performed to investigate the dependence of the pressure hill height and the influence zone expanse, for flow past a spiked body with different nose configurations, over a Reynolds number range from 2278 to 4405 to establish the vortex shedding process, and applicability in low speed flow regime for effective pressure reduction. It is found that the spike reduces the radius of curvature of the approaching streamline, leading to the deflection of the streamlines towards the shoulder of the basic body, resulting in a narrow zone of the positive pressure hill at the body nose. It is also observed that the pressure hill length and the influence zone expanse decrease with the introduction of spike over the present range of Reynolds numbers. For Reynolds numbers less than 2700, spike with conical nose is found to be more efficient than the spikes with other nose shapes of the present study in reducing the positive pressure at the nose of the blunt body. For higher Reynolds numbers, greater than 2700, the size of the vortex at the junction of the spike and basic body is the largest for the spike with hemispherical nose, and emerges as a potential candidate for application in possible wind-design resistant structures.

VIV Suppression Device Development and the Perils of Reynolds Number

2017 ◽  
Author(s):  
Don W. Allen ◽  
Nicole Liu
Keyword(s):  
Reynolds Number ◽  
Small Diameter ◽  
Reynolds Numbers ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Helical Strakes ◽  
Low Reynolds ◽  
Offshore Industry ◽  
High Reynolds ◽  
Viv Suppression

Most deepwater tubulars experiencing high currents frequently require vortex-induced vibration (VIV) suppression to maintain an acceptable fatigue life. While helical strakes and fairings are by far the most popular VIV suppression devices used in the offshore industry today, a myriad of small alternations to these basic devices can significantly impact the observed levels of suppression effectiveness. Additionally, numerous novel VIV reduction devices are continually being developed and some new devices are progressing towards the product readiness phase. It is quite common to first test suppression devices at low Reynolds numbers due to the availability of smaller scale facilities that are typically more budget-friendly than larger scale facilities. For larger scale testing, it is usually simpler and less expensive to evaluate prototype suppression devices on shorter pipe sections that are spring mounted rather than test on longer flexible pipes. This paper utilizes results from historical VIV experiments to evaluate the merits of various test setups and scales and to underscore the importance of Reynolds number. An assortment of testing scales are presented including: a) small diameter tests at low Reynolds numbers; b) moderate diameter tests that incorporate at least part of the critical Reynolds number range; c) short pipe tests conducted at prototype Reynolds numbers; and d) long pipe tests conducted at high Reynolds numbers but at less than full scale suppression geometry. The use of computational fluid dynamics (CFD) is also briefly discussed.

Asymmetries in the wake of a submarine model in pitch

2015 ◽  
Vol 774 ◽  
pp. 416-442 ◽  
Author(s):  
A. Ashok ◽  
T. Van Buren ◽  
A. J. Smits
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Relative Strength ◽  
The Body ◽  
Wind Tunnels ◽  
Body Of Revolution ◽  
Streamwise Vortices ◽  
Velocity Measurements ◽  
Mean Velocity ◽  
High Angles Of Attack

Detailed velocity measurements in the wake of a body of revolution are reported for pitch angles up to $12^{\circ }$, over an unprecedented range of Reynolds numbers ($2.4\times 10^{6}\leqslant \mathit{Re}_{L}\leqslant 30\times 10^{6}$). The body of revolution, an idealized submarine shape (DARPA SUBOFF), is mounted using a support that mimics a semi-infinite sail. The wake measurements at all pitch angles and Reynolds numbers reveal the presence of a pair of streamwise vortices of unequal strengths which tend to rotate around each other as they evolve downstream. Various attempts to perturb the upstream conditions on the body had no significant impact on the relative strength of the vortices. In addition, two different models, tested in two different wind tunnels, show similar asymmetries, and we propose that wake asymmetry appears to be a robust feature of this flow, a result previously only seen for sharp-nosed bodies at high angles of attack. It is also shown that the wake behaviour for $x/D>5$, in terms of the streamwise mean velocity and turbulence intensity distributions, appears to become invariant with Reynolds number for $\mathit{Re}_{L}>4.8\times 10^{6}$.

Experiments on the flow past a circular cylinder at low Reynolds numbers

1959 ◽  
Vol 6 (4) ◽  
pp. 547-567 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Experimental Evidence ◽  
Theoretical Calculations ◽  
Reynolds Numbers ◽  
Vortex Street ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Experimental Values

Part I describes measurements of the drag on circular cylinders, made by observing the bending of quartz fibres, in a stream with the Reynolds number range 0·5-100. Comparisons are made with other experimental values (which cover only the upper part of this range) and with the various theoretical calculations.Part II advances experimental evidence for there being a transition in the mode of the vortex street in the wake of a cylinder at a Reynolds number around 90. Investigations of the nature of this transition and the differences between the flows on either side of it are described. The interpretation that the change is between a vortex street originating in the wake and one originating in the immediate vicinity of the cylinder is suggested.

A Reassessment of Metering Orifices for Low Reynolds Numbers

1965 ◽  
Vol 180 (1) ◽  
pp. 331-356 ◽  
Author(s):  
L. J. Kastner ◽  
J. C. McVeigh
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Flow Rate ◽  
Discharge Coefficient ◽  
Low Reynolds Number ◽  
Reynolds Numbers ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Discharge Coefficients ◽  
Low Reynolds

In view of the importance of accurate measurement of flow rate at low Reynolds numbers, there have been numerous attempts to develop metering devices having constant discharge coefficients in the range of pipe Reynolds numbers between about 3000 and 200 and even below this latter value, and some of these attempts have achieved a reasonable degrees of success. Nevertheless, some confusion exists regarding the dimensions and range of utility of certain designs which have been recommended and further information is necessary in order that the situation may be clarified. The aims of the present investigation, which is believed to be wider in scope than any published in this field in recent years, were to review and correlate existing knowledge and to make an experimental study of the properties of various types of orifice in the low range of Reynolds numbers. Arising from this it was hoped that a design might be evolved which not only had a satisfactorily constant discharge coefficient throughout the range but was also simple to manufacture and reproduce, even for small orifice diameters of the order of 0.5 in or less, and it is believed that some success in attaining this aim was achieved. The first section of the paper contains a review of previous investigations classified into three main groups. In the second part of the paper, experiments with various types of orifice plate are described and it is shown that a properly proportioned single-bevelled orifice has as good a performance in the low Reynolds number range as that of any of the more complicated shapes.

Vortex shedding from spheres

1974 ◽  
Vol 62 (2) ◽  
pp. 209-221 ◽  
Author(s):  
Elmar Achenbach
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Critical Reynolds Number ◽  
Measurement Techniques ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Present Measurement ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
The Relationship

Vortex shedding from spheres has been studied in the Reynolds number range 400 < Re < 5 × 106. At low Reynolds numbers, i.e. up to Re = 3 × 103, the values of the Strouhal number as a function of Reynolds number measured by Möller (1938) have been confirmed using water flow. The lower critical Reynolds number, first reported by Cometta (1957), was found to be Re = 6 × 103. Here a discontinuity in the relationship between the Strouhal and Reynolds numbers is obvious. From Re = 6 × 103 to Re = 3 × 105 strong periodic fluctuations in the wake flow were observed. Beyond the upper critical Reynolds number (Re = 3.7 × 105) periodic vortex shedding could not be detected by the present measurement techniques.The hot-wire measurements indicate that the signals recorded simultaneously at different positions on the 75° circle (normal to the flow) show a phase shift. Thus it appears that the vortex separation point rotates around the sphere. An attempt is made to interpret this experimental evidence.

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